Influenza; Strep throat; Bird flu; Avian influenza
Differentiating between a cold and flu may be difficult. Cold symptoms are nearly always less severe than those of the flu.
Comparing Colds and Flus
Common and high (102 - 104 F); lasts 3 - 4 days
Almost always present
General aches and pains
Mild, if they occur at all
Fatigue, exhaustion, and weakness
Mild, it they occur at all
Extreme exhaustion is early and severe; can last 2 - 3 weeks
Chest discomfort and cough
Mild-to-moderate, hacking cough
Common, can be severe
Source: National Institute of Allergy and Infectious Disease
Several available tests can isolate and identify the viruses responsible for some respiratory infections. They are generally not needed, since most cases of the flu are self-evident. However, such tests can be very helpful in confirming or ruling out the flu. If a doctor believes a diagnosis would help, samples using a swab should be taken from the nasal passages or throat within 4 days of the first symptoms.
Several rapid tests for the flu can produce results in less than 30 minutes, but vary on the specific strain or strains that they can detect. They are not as accurate as a viral culture, however, in which the virus is reproduced in the laboratory. Culture results can take 3 - 10 days. Blood tests can also document the infection several weeks after symptoms appear.
In February 2006, the U.S. Food and Drug Administration approved a new, faster test for diagnosing H5 strains of avian influenza in people suspected of having the virus. The test is called the Influenza A/H5 (Asian lineage) Virus Real-time RT-PCR Primer and Probe Set. The test gives preliminary results within 4 hours. Older tests required 2 - 3 days. It checks for the presence of the Influenza A H5 strain. If the presence of this strain is confirmed through the rapid test, further testing will be needed to determine the exact subtype of the virus. For example, the current strain of concern is H5, subtype N1, designated as H5N1 for short.
Ruling out Allergic Rhinitis. Symptoms of allergic rhinitis include nasal obstruction and congestion, which are similar to the symptoms of a cold. People with allergies, however, are likely to have the following:
There are two forms of allergic rhinitis:
Ruling out Sinusitis. The signs and symptoms suggestive of true acute sinusitis include the following:
Children with sinusitis are less likely to have facial pain and headache and may only develop a high fever or prolonged upper respiratory symptoms (such as a daytime cough that does not improve for 11 - 14 days). When the diagnosis is unclear or complications are suspected, further tests may be required. [For more information, see In-Depth Report #62: Sinusitis.]
Acute Bronchitis. Acute bronchitis is usually caused by a virus and in most cases is self-limiting. The cough it causes typically lasts for about 7 - 10 days, but in about half of patients, coughing can last for up to 3 weeks, and 25% of patients continue to cough for over 1 month.
Atypical Pneumonia. Pneumonia caused by atypical organisms (for example, Mycoplasma pneumonia, chlamydia, Legionella) can cause symptoms similar to the flu. Only laboratory tests can diagnose the difference. [For more information, see In-Depth Report #64: Pneumonia.]
Ruling out other Viral Infections. Respiratory syncytial virus (RSV) and, possibly human parainfluenza viruses (HPV), are proving to be important causes of serious respiratory infections in infants, the elderly, and people with damaged immune systems. (Both also cause mild conditions.) RSV may be a much more common cause of flu-like symptoms than previously thought.
Pertussis. Pertussis (whooping cough) was a very common childhood illness throughout the first half of the century. Although immunizations caused a decline in cases to only 1,700 in the U.S. in 1980, the incidence has risen recently, with 8,739 cases in 2007. Many more cases are reported worldwide.
Nearly half of pertussis cases now occur in people 10 years of age or older, perhaps due to waning immunity in adolescents and adults. Such cases may be greatly underreported. Up to 25% of adults who see a doctor for persistent cough may actually have pertussis. It may go undiagnosed, however, because their symptoms are usually mild, and adults are unlikely to have the classic "whooping" cough. This is of some concern because such adults may unknowingly infect unvaccinated children. The younger the patient, the higher the risk for severe complications, including pneumonia, seizures, and even death. Children younger than 6 months are at particular risk because protection is incomplete, even with vaccination.
In April 2005, the FDA approved the first pertussis-containing booster vaccine ("Boostrix") for children aged 10 - 18. In December 2008, the FDA approved this vaccine for use in adults up to age 64.
In addition to common cold viruses, other, less frequent causes of sore throat include the following:
Group A Streptococcal bacteria is the most common bacterial cause of the severe sore throat known commonly as "strep throat." It occurs mostly in school age children, but people of all ages are susceptible. (Strep throat constitutes about 12% of all sore throat cases seen by doctors.)
The symptoms of strep throat include the following:
Only about half of patients with strep throat have such clear-cut symptoms. Furthermore, half of people who have these symptoms do not actually have strep throat.
How Is Strep Throat Diagnosed? Most cold-related sore throats are caused by viruses and require no treatment. They usually do not last more than a day. When the sore throat persists and is very painful the doctor will want to rule out or confirm the presence of the Streptococcus bacteria.
A throat culture is the most effective and least expensive test for confirming the presence of strep throat. It takes 24 - 48 hours to obtain a result.
Rapid Antigen-Detection Test for Strep Throat. A faster test, called the rapid strep antigen test, uses chemicals to detect the presence of bacteria in a few minutes. A positive result nearly always means that streptococcal bacteria are the cause of the infection. The test, however, fails to detect 5 - 10% of cases, so a culture may still be necessary to catch any missed infections, particularly in children.
How Serious is Strep Throat? The use of antibiotics has removed the threat of most complications from streptococcus infection in the throat. However, untreated strep throat could lead to the following complications:
How Is Strep Throat Treated? Strep throat infections require antibiotics. Antibiotics prevent a serious complication called rheumatic fever, which can result in permanent damage to the heart. Fortunately, this complication rarely occurs in United States anymore. If started on time, antibiotic treatment of strep throat will almost always prevent this complication. In addition, antibiotics shorten the recovery time from strep throat.
The following antibiotics are generally used to treat strep throat:
Antibiotics are very often inappropriately prescribed for non-strep sore throats. Studies indicate that fewer than half of adults and far fewer of the children with even strong signs and symptoms for strep throat actually have strep infections.
Parents should be comforted that a delay in antibiotic treatment while waiting for lab results does not increase the risk that the child will develop serious long-term complications, including acute rheumatic fever. If a patient is severely ill, however, it is reasonable to begin administering antibiotics before the results are back. If the culture is negative (there is no evidence of bacteria), the doctor should call the family to make certain the patient stops taking the antibiotics and any remaining pills are discarded.
Children who have a sore throat and who have had rheumatic fever in the past should receive antibiotics immediately, even before culture results are back. Children with a sore throat who have a family member with strep throat or rheumatic fever should also receive immediate antibiotic treatment.
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